Mishkat al-Masabih 15 Oaths and Vows كتاب الإيمان والنذور 9

وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «وَاللَّهِ لَأَنْ يَلَجَّ أَحَدُكُمْ بِيَمِينِهِ فِي أَهْلِهِ آثَمُ لَهُ عِنْدَ الله نم أَنْ يُعْطِيَ كَفَّارَتَهُ الَّتِي افْتَرَضَ اللَّهُ عَلَيْهِ»

He reported God’s Messenger as saying, “I swear by God that it is more sinful in God’s sight for one of you to persist in his oath regarding his family than to give for it the atonement God has imposed.” (Bukhari and Muslim.)